1. Field of the Invention
The present invention relates to a composite planetary gear apparatus, and in particular to a composite planetary gear apparatus incorporating therein two planetary gear assemblies for reduction of the rotation speed of a drive power shaft having a drive power outputted by an engine.
2. Description of the Background Art
Up until now, there has been known as a prior-art composite planetary gear apparatus of this kind an apparatus to be mounted on a hybrid automotive vehicle, for example, by a following patent document. The known composite planetary gear apparatus is constituted by a first planetary gear assembly used for reduction of the output speed of a drive motor, and a second planetary gear assembly having a drive power distribution function to distribute a drive power outputted from an engine to a motor generator and to a counter drive gear serving as an integral part of outer ring member. The first planetary gear assembly and the second planetary gear assembly have sun gears and pinion gears, respectively, and have a common counter drive gear having a pair of inner teeth formed in coaxial relationship with the respective sun gears and held in mesh with the respective pinion gears and outer teeth formed on the outer peripheral portion thereof.
The conventional composite planetary gear apparatus is constructed as being supplied with an oil circulated from a catch tank and an oil pumped from an oil pump through a plurality of oil passageways formed in rotation shafts, respectively, in the sun gears, to be held in communication with the inner peripheral surfaces of the sun gears, respectively, and then having the oil from the catch tank and the oil pump to be stirred with the rotations of a plurality of gears constituting the composite planetary gear apparatus for the purpose of lubricating parts and elements forming part of the composite planetary gear apparatus.
More specifically, there is shown in FIG. 5 a composite planetary gear apparatus 80 which comprises a first gear assembly 81 and a second gear assembly 82 forming in combination a closed space A1 in a counter drive gear 83. The closed space A1 is adapted to be fed with oil from a catch tank and an oil pump as shown by the arrows F1 and F2 in FIG. 5. The respective rotations of ring gears R1, R2 and pinion gears P1, P2 cause the oil to be stirred in the closed space A1 for lubricating the parts and elements forming the composite planetary gear apparatus 80.
Patent Document: Laying-open patent publication No. 2005-308094
The conventional composite planetary gear apparatus 80, however, encounters such a problem that when the oil is fed into the composite planetary gear apparatus 80, the oil entered the closed space A1 is radially outwardly urged by the centrifugal force of the oil toward the inner peripheral surface of the counter drive gear 83 by the reason that the first gear assembly 81 and the second gear assembly 82 forms in combination the closed space A1 in the counter drive gear 83. The radially outwardly urged oil is difficult to be discharged out of the closed space A1 and remains stagnantly in the closed space A1. As a consequence, the stagnantly remaining oil leads to imparting resistance to the rotations of the planetary gears, thereby resulting in increasing the stirring loss and lowering fuel efficiency of the engine.